Communications systems using conventional multiple-input multiple-output (MIMO) technology exploit spatial diversity at the transmitter and at the receiver to increase throughput compared to a single-input single-output (SISO) system. In a wire-line MIMO system, multiple physical channels may be defined using conductors of a communications medium. For example, a powerline may have three conductors (e.g., a line or hot wire, a neutral wire, and a ground or protective earth wire) bundled together in a sheath. A wire pair consisting of two conductors may be used together to define a physical channel. To implement MIMO for powerline communications (PLC), two of the conductors may be used to carry signals while a third conductor may serve as a reference for both of the two signal-carrying conductors. As such, it is possible to have two physical channels in MIMO for PLC.
Current technologies for utilizing a multichannel communications medium may employ complex techniques to pre-condition the transmitted information into two distinct channels of information. For example, in one approach referred to as beamforming, the receiver may compute a pre-coding matrix corresponding to each active carrier and send it to the transmitter. The transmitter may use complex coding and digital signal processing to prepare two different streams of information to transmit via the multichannel communications medium. Despite the use of two different streams of information, the throughput may drop due to lower transmit power for each stream of information or due to cross-talk between the physical channels. Furthermore, the digital signal processing components may add to the cost and complexity of devices implementing beamforming.